Dave's Falls County Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dave's Falls County Park clear sky chart from 2005-11-06 to 2025-10-04.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	13% 9% 3 8% 5% 5% 5% 4 5% 7% 37%	126752
	Night	13% 10% 4 8% 5% 4 4 3 5% 7% 37%	122912
Transparency	Day	45% 6% 12% 23% 12% 1	130214
	Night	45% 6% 13% 23% 12% 1	127524
Seeing	Day	18% 15% 32% 22% 10% 3	17327
	Night	18% 10% 33% 28% 9% 1	27132

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	9% 10% 4 11% 7% 6% 6% 4 6% 6% 30%	3617
	11th to 20th	Day	12% 11% 4 8% 6% 5% 5% 5% 7% 7% 29%	3620
	21st to end	Day	11% 16% 5% 12% 5% 4 4 3 5% 6% 29%	3982
February	1st to 10th	Day	9% 12% 4 9% 6% 5% 4 3 6% 7% 35%	1719
	11th to 20th	Day	10% 12% 4 10% 6% 4 5% 4 5% 6% 35%	1894
	21st to end	Day	12% 14% 5% 8% 5% 3 4 4 6% 6% 33%	1650
March	1st to 10th	Day	12% 9% 2 5% 4 3 4 3 5% 7% 45%	4480
	11th to 20th	Day	11% 10% 3 9% 6% 6% 5% 4 6% 7% 33%	4682
	21st to end	Day	23% 12% 4 10% 5% 4 4 2 3 4 27%	5967
April	1st to 10th	Day	16% 14% 4 8% 6% 5% 4 5% 5% 6% 28%	2400
	11th to 20th	Day	20% 10% 3 7% 5% 5% 5% 3 5% 6% 32%	2374
	21st to end	Day	19% 9% 3 7% 4 5% 6% 3 5% 6% 33%	2595
May	1st to 10th	Day	13% 6% 2 7% 4 4 4 3 4 5% 46%	6082
	11th to 20th	Day	11% 7% 3 7% 5% 5% 4 4 6% 7% 41%	6319
	21st to end	Day	14% 8% 3 8% 5% 5% 5% 4 6% 7% 36%	6935
June	1st to 10th	Day	12% 6% 2 6% 5% 5% 4 4 6% 8% 42%	2800
	11th to 20th	Day	15% 6% 2 7% 6% 5% 5% 4 6% 7% 37%	2800
	21st to end	Day	13% 7% 2 6% 5% 4 5% 4 7% 8% 38%	2800
July	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 4 6% 9% 42%	6360
	11th to 20th	Day	8% 4 2 5% 4 5% 5% 4 6% 9% 49%	6360
	21st to end	Day	9% 5% 2 6% 4 5% 5% 4 6% 9% 45%	6924
August	1st to 10th	Day	9% 5% 3 8% 6% 5% 6% 4 7% 9% 39%	4563
	11th to 20th	Day	12% 5% 2 6% 4 4 4 4 5% 7% 48%	4160
	21st to end	Day	14% 6% 2 7% 4 5% 5% 4 5% 7% 42%	4312
September	1st to 10th	Day	12% 6% 2 7% 5% 4 4 4 6% 7% 43%	2400
	11th to 20th	Day	11% 5% 2 6% 4 6% 5% 5% 6% 9% 42%	2285
	21st to end	Day	12% 6% 2 8% 5% 5% 6% 5% 7% 8% 37%	2200
October	1st to 10th	Day	15% 6% 2 7% 4 4 5% 4 6% 7% 39%	2038
	11th to 20th	Day	20% 11% 3 8% 5% 6% 4 3 6% 8% 27%	1826
	21st to end	Day	21% 10% 3 8% 5% 5% 5% 4 4 6% 30%	1881
November	1st to 10th	Day	14% 10% 3 8% 4 4 5% 4 4 7% 38%	1762
	11th to 20th	Day	15% 12% 5% 8% 7% 5% 5% 4 6% 7% 27%	1765
	21st to end	Day	15% 13% 4 8% 5% 4 5% 4 7% 8% 29%	1600
December	1st to 10th	Day	10% 14% 5% 10% 6% 6% 6% 4 6% 7% 27%	2610
	11th to 20th	Day	14% 17% 4 10% 5% 5% 5% 4 5% 6% 26%	3008
	21st to end	Day	23% 21% 6% 10% 4 3 3 2 4 5% 20%	3982
January	1st to 10th	Night	9% 12% 5% 11% 6% 4 5% 3 5% 6% 34%	6348
	11th to 20th	Night	9% 15% 6% 11% 7% 5% 5% 4 5% 7% 26%	6360
	21st to end	Night	9% 14% 7% 11% 5% 4 5% 4 5% 6% 31%	6996
February	1st to 10th	Night	10% 13% 5% 10% 6% 6% 4 3 5% 6% 33%	2680
	11th to 20th	Night	10% 11% 4 9% 6% 4 5% 3 6% 7% 35%	2391
	21st to end	Night	14% 14% 4 8% 5% 4 4 4 5% 5% 34%	1980
March	1st to 10th	Night	13% 8% 2 7% 4 3 4 3 5% 7% 44%	5373
	11th to 20th	Night	10% 10% 3 8% 4 5% 5% 4 6% 9% 34%	5322
	21st to end	Night	21% 10% 4 8% 5% 5% 5% 3 5% 6% 29%	4962
April	1st to 10th	Night	19% 11% 3 9% 5% 4 5% 2 5% 7% 31%	2000
	11th to 20th	Night	21% 8% 3 6% 4 3 3 4 5% 6% 37%	1975
	21st to end	Night	17% 8% 3 7% 5% 5% 4 3 5% 7% 36%	1803
May	1st to 10th	Night	15% 7% 2 7% 4 4 4 3 5% 6% 44%	3818
	11th to 20th	Night	10% 9% 2 6% 5% 4 4 3 5% 7% 45%	3596
	21st to end	Night	18% 7% 2 6% 4 4 4 4 5% 6% 40%	3942
June	1st to 10th	Night	11% 5% 2 5% 5% 5% 4 4 5% 8% 46%	1600
	11th to 20th	Night	14% 7% 3 7% 4 4 5% 4 7% 7% 37%	1600
	21st to end	Night	15% 6% 2 5% 4 3 5% 4 6% 9% 43%	1600
July	1st to 10th	Night	12% 5% 2 5% 3 4 5% 4 5% 8% 47%	3618
	11th to 20th	Night	9% 3 2 4 3 3 4 3 5% 8% 56%	3617
	21st to end	Night	8% 5% 2 6% 4 4 4 4 5% 7% 51%	3947
August	1st to 10th	Night	11% 6% 2 7% 5% 4 4 3 5% 8% 46%	2597
	11th to 20th	Night	11% 4 2 6% 4 4 4 3 6% 7% 49%	2886
	21st to end	Night	11% 6% 2 6% 4 4 4 3 4 6% 49%	3586
September	1st to 10th	Night	10% 5% 2 6% 3 4 3 4 4 7% 53%	2000
	11th to 20th	Night	12% 4 2 5% 4 4 4 4 4 7% 50%	2095
	21st to end	Night	14% 6% 2 7% 3 3 3 3 5% 8% 45%	2200
October	1st to 10th	Night	15% 6% 2 5% 4 3 5% 4 6% 7% 45%	2206
	11th to 20th	Night	16% 11% 3 8% 4 4 4 4 5% 6% 35%	2353
	21st to end	Night	20% 10% 3 6% 5% 4 4 3 5% 7% 32%	2717
November	1st to 10th	Night	15% 9% 3 6% 4 4 4 3 5% 7% 39%	2536
	11th to 20th	Night	15% 11% 3 9% 5% 5% 4 3 5% 7% 33%	2633
	21st to end	Night	15% 12% 4 8% 5% 6% 5% 4 5% 6% 31%	2800
December	1st to 10th	Night	14% 10% 4 7% 5% 4 5% 4 7% 7% 33%	4580
	11th to 20th	Night	13% 15% 6% 11% 7% 5% 4 3 4 4 27%	5199
	21st to end	Night	23% 16% 5% 8% 4 3 3 2 5% 5% 24%	6996

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	52% 6% 13% 20% 9% 1	3618
	11th to 20th	Day	52% 7% 11% 19% 10% 2	3620
	21st to end	Day	56% 5% 12% 14% 12% 1	3982
February	1st to 10th	Day	48% 6% 14% 19% 12% 1	1719
	11th to 20th	Day	47% 7% 13% 22% 10% 1	1904
	21st to end	Day	50% 6% 11% 20% 11% 2	1650
March	1st to 10th	Day	38% 4 15% 20% 17% 5%	4480
	11th to 20th	Day	48% 6% 14% 21% 10% 2	4682
	21st to end	Day	61% 5% 8% 14% 12%	5969
April	1st to 10th	Day	55% 6% 12% 18% 9% 1	2400
	11th to 20th	Day	52% 6% 9% 20% 11% 1	2374
	21st to end	Day	50% 7% 10% 18% 14% 2	2595
May	1st to 10th	Day	38% 6% 11% 25% 17% 3	6117
	11th to 20th	Day	39% 8% 12% 26% 15% 1	6323
	21st to end	Day	44% 7% 10% 20% 17% 2	6949
June	1st to 10th	Day	37% 8% 14% 25% 15% 2	2800
	11th to 20th	Day	44% 7% 14% 19% 14% 1	2800
	21st to end	Day	41% 9% 15% 23% 12% 1	2800
July	1st to 10th	Day	37% 6% 14% 32% 10% 1	6291
	11th to 20th	Day	30% 7% 13% 36% 13% 1	6285
	21st to end	Day	34% 6% 13% 29% 16% 1	6728
August	1st to 10th	Day	40% 9% 14% 23% 14% 1	4548
	11th to 20th	Day	35% 6% 16% 30% 12%	4200
	21st to end	Day	41% 7% 15% 22% 14% 1	4311
September	1st to 10th	Day	39% 8% 14% 27% 13% 1	2400
	11th to 20th	Day	37% 9% 18% 28% 8%	2285
	21st to end	Day	42% 8% 14% 27% 9%	2200
October	1st to 10th	Day	31% 5% 13% 28% 22%	3363
	11th to 20th	Day	50% 4 10% 23% 13%	3016
	21st to end	Day	51% 6% 14% 22% 7%	3081
November	1st to 10th	Day	45% 6% 13% 24% 11%	1762
	11th to 20th	Day	55% 8% 13% 16% 8% 1	1765
	21st to end	Day	52% 9% 16% 18% 4 1	1600
December	1st to 10th	Day	55% 7% 14% 20% 5%	2610
	11th to 20th	Day	58% 6% 10% 14% 11% 1	3005
	21st to end	Day	67% 4 6% 16% 6%	3982
January	1st to 10th	Night	50% 5% 10% 25% 9% 1	6348
	11th to 20th	Night	56% 6% 11% 14% 12% 1	6360
	21st to end	Night	53% 6% 13% 17% 10%	6996
February	1st to 10th	Night	52% 4 11% 19% 12% 2	2680
	11th to 20th	Night	47% 6% 12% 22% 11% 2	2392
	21st to end	Night	51% 5% 13% 20% 9% 1	1980
March	1st to 10th	Night	39% 5% 19% 21% 14% 2	5373
	11th to 20th	Night	44% 7% 17% 21% 10% 1	5322
	21st to end	Night	54% 6% 11% 16% 11% 1	4962
April	1st to 10th	Night	53% 6% 10% 15% 15% 1	2000
	11th to 20th	Night	48% 5% 10% 22% 12% 2	1975
	21st to end	Night	47% 6% 12% 20% 13% 2	1803
May	1st to 10th	Night	40% 6% 11% 26% 14% 3	3845
	11th to 20th	Night	37% 8% 12% 24% 17% 2	3597
	21st to end	Night	43% 7% 11% 23% 12% 4	3950
June	1st to 10th	Night	35% 7% 13% 28% 15% 1	1600
	11th to 20th	Night	43% 7% 12% 22% 14% 1	1600
	21st to end	Night	37% 7% 15% 27% 12% 2	1600
July	1st to 10th	Night	35% 6% 17% 29% 11% 2	3580
	11th to 20th	Night	26% 5% 18% 35% 14% 2	3572
	21st to end	Night	31% 7% 15% 27% 20% 1	3832
August	1st to 10th	Night	37% 7% 14% 22% 18% 2	2588
	11th to 20th	Night	34% 8% 14% 29% 13% 2	2912
	21st to end	Night	36% 5% 14% 26% 17% 1	3586
September	1st to 10th	Night	32% 7% 14% 31% 16%	2000
	11th to 20th	Night	33% 7% 15% 34% 11%	2095
	21st to end	Night	38% 6% 16% 28% 11% 1	2200
October	1st to 10th	Night	31% 5% 11% 35% 16% 2	3661
	11th to 20th	Night	39% 5% 13% 27% 15%	3902
	21st to end	Night	50% 5% 12% 24% 10%	4467
November	1st to 10th	Night	45% 6% 13% 23% 12%	2536
	11th to 20th	Night	50% 6% 14% 18% 10%	2633
	21st to end	Night	52% 7% 15% 21% 5% 1	2800
December	1st to 10th	Night	48% 7% 22% 19% 4	4580
	11th to 20th	Night	61% 5% 10% 16% 9%	5201
	21st to end	Night	62% 5% 8% 16% 9%	6996

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	18% 15% 37% 21% 7% 1	300
	11th to 20th	Day	24% 17% 34% 21% 3 1	300
	21st to end	Day	22% 15% 43% 16% 4	330
February	1st to 10th	Day	16% 26% 39% 13% 5% 1	300
	11th to 20th	Day	19% 27% 36% 14% 4	300
	21st to end	Day	24% 22% 42% 10% 2	249
March	1st to 10th	Day	19% 26% 42% 10% 3	300
	11th to 20th	Day	21% 21% 36% 15% 6%	330
	21st to end	Day	28% 18% 28% 18% 8%	550
April	1st to 10th	Day	27% 19% 31% 17% 5% 1	500
	11th to 20th	Day	28% 20% 27% 16% 8% 1	492
	21st to end	Day	26% 17% 28% 20% 8% 2	500
May	1st to 10th	Day	21% 21% 30% 19% 7% 3	593
	11th to 20th	Day	18% 18% 35% 20% 7% 2	725
	21st to end	Day	18% 16% 30% 24% 8% 5%	789
June	1st to 10th	Day	12% 17% 35% 24% 10% 3	730
	11th to 20th	Day	19% 12% 35% 22% 9% 2	730
	21st to end	Day	17% 12% 32% 26% 9% 3	730
July	1st to 10th	Day	9% 9% 31% 32% 15% 5%	721
	11th to 20th	Day	9% 10% 35% 27% 14% 5%	718
	21st to end	Day	7% 9% 34% 29% 15% 6%	794
August	1st to 10th	Day	9% 8% 31% 28% 18% 6%	726
	11th to 20th	Day	12% 8% 24% 28% 19% 8%	570
	21st to end	Day	15% 10% 25% 24% 20% 7%	583
September	1st to 10th	Day	16% 11% 27% 25% 14% 7%	530
	11th to 20th	Day	12% 7% 26% 32% 19% 4	530
	21st to end	Day	17% 14% 24% 27% 15% 3	530
October	1st to 10th	Day	20% 16% 30% 19% 13% 1	417
	11th to 20th	Day	25% 23% 32% 17% 3	300
	21st to end	Day	29% 20% 35% 13% 3	330
November	1st to 10th	Day	18% 19% 37% 17% 7% 1	300
	11th to 20th	Day	22% 23% 33% 15% 5% 1	300
	21st to end	Day	21% 22% 39% 12% 6%	300
December	1st to 10th	Day	18% 18% 39% 19% 5% 1	300
	11th to 20th	Day	23% 23% 36% 14% 4	300
	21st to end	Day	30% 19% 32% 14% 3 1	330
January	1st to 10th	Night	16% 12% 42% 25% 5%	1000
	11th to 20th	Night	20% 13% 38% 23% 6% 1	1000
	21st to end	Night	18% 10% 39% 24% 7% 1	1100
February	1st to 10th	Night	16% 14% 40% 24% 6%	1000
	11th to 20th	Night	17% 17% 37% 23% 5%	836
	21st to end	Night	20% 14% 39% 24% 3	660
March	1st to 10th	Night	17% 13% 36% 27% 7%	800
	11th to 20th	Night	15% 16% 42% 21% 5%	790
	21st to end	Night	19% 11% 35% 28% 7% 1	660
April	1st to 10th	Night	22% 13% 35% 24% 5%	600
	11th to 20th	Night	26% 11% 29% 27% 7%	593
	21st to end	Night	20% 11% 32% 29% 8%	600
May	1st to 10th	Night	22% 11% 30% 30% 7% 1	600
	11th to 20th	Night	19% 11% 33% 30% 6% 1	591
	21st to end	Night	16% 8% 30% 34% 12%	650
June	1st to 10th	Night	13% 8% 30% 40% 10%	600
	11th to 20th	Night	18% 7% 28% 36% 10% 1	600
	21st to end	Night	16% 6% 26% 39% 13% 1	600
July	1st to 10th	Night	8% 4 24% 45% 19% 1	585
	11th to 20th	Night	9% 4 29% 40% 18%	582
	21st to end	Night	10% 4 29% 38% 18% 2	657
August	1st to 10th	Night	10% 3 25% 40% 21% 2	597
	11th to 20th	Night	10% 3 23% 39% 24% 2	594
	21st to end	Night	13% 5% 23% 38% 20% 1	660
September	1st to 10th	Night	12% 6% 26% 32% 21% 3	600
	11th to 20th	Night	13% 5% 29% 31% 20% 2	695
	21st to end	Night	17% 8% 28% 30% 16% 1	800
October	1st to 10th	Night	18% 11% 29% 28% 13% 1	773
	11th to 20th	Night	20% 13% 34% 24% 7%	760
	21st to end	Night	26% 11% 32% 24% 7%	836
November	1st to 10th	Night	20% 11% 37% 26% 6% 1	780
	11th to 20th	Night	20% 16% 36% 21% 6%	833
	21st to end	Night	21% 14% 34% 26% 5%	1000
December	1st to 10th	Night	21% 14% 39% 21% 6% 1	1000
	11th to 20th	Night	20% 13% 35% 24% 6% 1	1000
	21st to end	Night	27% 11% 36% 22% 4	1100

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